Insertion Reactions of Metal Complexes

Abstract

The insertion reaction is encountered with surprising frequency in organometallic chemistry. Many types of unsaturated molecules undergo the reaction with many different metal compounds. For example, compounds containing metal-hydrogen, metal-carbon, metal-oxygen, metal-nitrogen, metal-halogen, and metal-metal bonds have reacted with one or more of the following unsaturated compounds: carbon monoxide, olefins, dienes, acetylenes, carbonyl compounds, and cyanides. There are still many gaps in our knowledge of the insertion reaction, but already it has been applied in numerous unusual and useful chemical syntheses.Jhe reaction mechanism of the various metal complexes clearly have much in common.The recently recognized insertion reaction appears to be a parti cularly good example of a reaction which is general among the metal compounds.In the following discussion I intend to point out the generality of the insertion reaction with examples from the literature and from our own work. The most complete series of substantiated insertion reactions involves the organocobalt carbonyl complexes, and these reactions will form the nucleus of the discussion. The insertion reaction is the addition of a covalent metal compound, M-X, to a neutral unsaturated molecule, :Y, forming a new complex where the unsaturated molecule has inserted itself between the metal and the atom which was initially bonded to the metal. M-Z + :Y -> M-Y-ZThe unsaturated molecule :Y may be carbon monoxide, an olefin, a conjugated diene, an acetylene, a carbonyl compound, various unsaturated carbon-nitrogen compounds, or probably any of several other unsaturated materials. The reactive part of the covalent metal compound is usually a metal-hydrogen, metal-carbon, metal-oxygen, metal-halogen, metal-nitrogen, or metal-metal group. This reaction

Electrophilic behavior of tetracyanoethylene toward transition metal-carbon .sigma. bonds. Reactions with alkyl complexes

“…Synthesis and Characterization of New Complexes. Reactions of TCNE with transition metal compounds containing M-C bonds yielded new tetracyanoethylene-containing complexes of three types: (1) metal cyanoalkyls (I; complexes [1][2][3][4][5][6][7] in Tables II and III), (2) metal keteniminates (II; complexes 8-14, 18, and 19 in Tables II and III), and (3) metal-tetracyanoethylene acyls (III; complexes 21-25 in Tables II and III). Alkyl compounds of formulas 7,5-CsH5Fe(CO)2R and t,5-C5H5Mo(CO)2(L)CH3 (L = P(C6H5)3 and P(OC6H5)3) afford both I and II upon reaction with TCNE, whereas 7j5-C5H5Fe(CO)(L)R (L = phosphine and phosphite) yield either II or III, depending on the group R. Molybdenum alkyls of the type t,5_c5H5Mo(CO)3R (R = CH3 and CH2C6H5) were found to undergo insertion reaction with TCNE extremely slowly and with considerable decomposition.…”